1. Field of Invention
The present invention relates to inverter-type or flyback converter-type magnetron power supplies for microwave ovens.
2. Prior Art
Power-line-operated electronic inverter-type magnetron power supplies have been previously described, such as in U.S. Pat. No. 3,973,165 to Hester, or in U.S. Pat. No. 4,002,875 to Kiuchi et al. However, these previously described power supplies have not addressed, let alone resolved, a basic issue associated with the practical application of such power supplies. This basic issue relates to the crest-factor of the current supplied to the magnetron--the crest-factor being the ratio of peak to average current.
It is necessary that the power delivered to the magnetron be delivered with an acceptably good crest-factor; otherwise, the magnetron--due to limits on cathode emissivity and associated moding effects--would not be able to supply the required level of microwave output power.
In particular, for practical reasons, it is necessary that the magnetron be supplied with a current of crest-factor not any poorer than what is presently being provided by most commonly used transformer-type magnetron power supplies; the typical crest-factor of which is about 3.5.